After the war, Kingsley's last act in office is to give Harry extrajudicial powers to be the guardian of magical Britain, if necessary to stop the Ministry from repeating 1997 and to stop people from getting away with loopholes and such. Very quickly, this turns out to be a curse rather than a blessing. Few people are trusting Harry given the extend of his powers, and his methodical pursuit of former Death Eaters only fuels that sentiment
It gets lonely over time, Hermione is a workaholic, Ron and Ginny are professional Quidditch players and Harry sees his friends far less than he'd like. Ron shows up with a new girlfriend each time they meet, Neville is plant crazy and Hermione is on the edge of burnout. It was then that Harry ran into an old acquaintance.